Day and Night program allows to see the Earth from the space.
It displays the line of demarcation between hemisphere lit by the sun and the shadow zone (terminator).
Moreover it draws the bounds of all continents: those lit by the sun are outlined by white colour while those in shadow area are outlined by grey.
Once inserted longitude and latitude the observer will be placed at the zenith of those coordinates.
It is possible to set any date, time and geographical site. The user can simulate terrestrial rotation but he will turn together the Earth. This is possible by using ''Real auto refresh'': the program will generate new configuration based on internal clock; ''Simulate auto refresh'' allows to generate new configuration based on time (hour) that the user insert in start form of the program.
The program shows ''Equator'', Greenwich meridian, Polar circles. It is possible to see the evolution of the seasons and to understand the period of the year according to the position of the demarcation line (terminator).
When terminator is tangent to North polar circle and this is lit by the sun we are on Summer solstice (near 21th June); if the North Pole is not lit by the Sun we are on Winter solstice (near 21 December). When terminator crosses North or South Pole we are on Equinoxes (near 21th March or 21th September).
The values of observer's zenith point (zObs) and those of the Sun (with reference to terrestrial coordinates - the Sun will be at the zenith of those coordinates, its declination coincide with latitude value) will be displayed.
To convert all geographical coordinates to Palm coordinates is necessary a lot of CPU resource: on Tungsten T3 (the faster Palm OS model) the program spends about 40 seconds to generate a complete configuration. The user can see, step by step, the realization of the Earth's map.
Version 1.1 of the program allows to select resolution value between 0 (minimum) up to 7 (maximum resolution). By using resolution 0 on Tungsten T3 the program spends about 18 seconds to complete the map, but the continent bound are to poor. To accelerate the draw of the map it is possible to choose ALL continents or just one from the list on the right.